# Tag Info

Accepted

### Why is a half-streamlined body less aerodynamic?

The drag coefficients are normalized by a reference area. For something like this, it is going to be the frontal area. So, if the streamlined body and half-body had the same frontal area, the drag on ...
• 13.1k

### Why does turbulence over a wing make drag?

Short answer: turbulent flow causes vigorous mixing of the flow nearest the wing with flow further away from the wing. this tends to share the energy imparted from the wing to the airflow nearest the ...
• 21.3k

### Cause of Drag From Windmilling

a windmilling prop is extracting work from the air moving through the prop disc, and using that work to rotate the dead engine. the power extracted is approximately equal to the speed of the air times ...
• 21.3k

### In a straight and level flight if thrust is equal to drag how is aircraft moving forward?

Per Newton's first law, A body remains at rest, or in motion at a constant speed in a straight line, except insofar as it is acted upon by a force. You need excess thrust to get up to speed. But ...
• 13.4k

### Why does turbulence over a wing make drag?

Stop thinking about the direction of the velocity as a force pushing on a wing. Velocity is not a force. Stop it, you're making yourself confused. Turbulence has different meanings. Normal people (...
• 13.1k

### Drag breakdown of a typical civil airplane wing

At best L/D, an aircraft (with a simple parabolic polar) has half induced and half parasite drag. If half the parasite drag is from the fuselage -- and you are flying at best L/D, then we can say that ...
• 13.1k

### Can there be interference drag in inviscid flow?

A non-lifting body in inviscid flow can have induced drag if there is lift (that cancels) on parts of the body. Imagine two rectangular, untwisted wings with symmetrical airfoils -- arranged in a ...
• 13.1k

### How does the lift-to-drag ratio depend on absolute sizes?

Does $\varepsilon$ or $C_{D,0}$ depend on absolute sizes? $\epsilon$ is in the range 0 to 1 and mainly depends on the spanwise lift distribution, so it does not directly depend on the global size of ...
• 13.5k
Accepted

### Can there be interference drag in inviscid flow?

If you assume the flow to be incompressible, inviscid and stationary then the Navier-Stokes equations reduce to the Laplace's equation and the relevant aerodynamic force posseses no drag if the body ...
• 13.5k

### In which position does Starship wings produce the most drag?

Because the Starship falls horizontally you are correct to have Cdrag rather than Clift in your equation. Based on coefficient of drag shapes here, having the fins canted down may produce more drag, ...
• 20.6k

### Minimum sink speed and maximum endurance speed

It depends on the characteristics of the engine. Minimum sink speed is the speed for minimum power required. If your fuel consumption is generally proportional to power, then yes it should be very ...
• 13.1k
Accepted

### How does drag change efficient cruise conditions?

The easiest way to reduce induced drag in an aircraft is to make it lighter. However, I'll assume you're talking about design / configuration changes, not operational ones. If the drag polar has the ...
• 13.1k

### Why is a half-streamlined body less aerodynamic?

The numbers given in the table are coefficients, not force values. They have to be referenced to a given frontal cross-section area. The wrong way to interpret the table: "If I take a ...
• 22.7k

### Thrust needed to overcome parasite drag that increases with speed

Drag is a force. Thrust is a force. The extra thrust needed to overcome the added parasite drag is proportional to the amount of that added parasite drag. But power is proportional to thrust times ...
• 22.7k

### Why induced drag shows up as reduced pressure downstream of the wing?

In a wind tunnel, drag shows up as a reduction of the speed (momentum to be precise) of the airstream behind the body. The drag that normally appears in any plot of the aerodynamic coefficients, is ...
• 13.5k

### Are there studies to find surface treatments to reduce the drag of an airfoil?

Yes, there are literally thousands of studies on the subject. A keyword search on this link brings up many examples. (credit to Sophit) There's also a similar question on this site that may be ...
• 26.9k

### How does drag change efficient cruise conditions?

We use the usual approximation that the drag coefficient for the entire airplane can be expressed via the well known: $C_d=C_{d_0}+kC²_l$ The first term represents the "parasite drag" while ...
• 13.5k
Accepted

### Forces acting on ram air parachute (for pulling ships)

Two perpendiculars make 180 degrees, force opposite the ships drag. It's the same with iceboats. Instead of using wind as propulsion, wind is used to move the sail. The lift from the sail (more ...
• 20.6k

### Does the cross-sectional shape of a fuselage affect drag?

The quadratic body has more surface area compared to the round body, so this alone will guarantee a higher friction drag. If the angles of attack and sideslip were always zero and no lift is created, ...
• 234k
Accepted

### Does CG change airspeed in a descent or glide?

Moving the CG forward will result in a negative $∆C_m$ (nose-down moment) for the wing, with minor effect on the tailplane $C_m$, which depends on the direction of its loading. So yes, if the original ...
• 3,346

### Why is a half-streamlined body less aerodynamic?

This is a typical example where a picture is worth a thousand words... or is it? This picture is a potpourri of several experiments, some of them performed and recorded in very old NACA reports. The ...
• 13.5k

### Why is a half-streamlined body less aerodynamic?

In terms of drag coefficient, it is important to have "clean", undisturbed air flowing over a surface to minimize drag. The half airfoil shape near the ground has a higher coefficient of ...
• 20.6k

### Why does turbulence over a wing make drag?

Let's slightly change your concept and reframe your thinking, if that is ok. Think of drag as the wing dragging air in the direction of flight. Now think of the process by which that would happen. ...
• 1,390

### Determining Sectional Drag Coefficient Using Propeller Geometry

I'm trying to teach myself blade element theory for helicopters and propellers, but I'm getting quite confused. Advanced aerodynamics is nothing that you can teach yourself unless you have a good ...
• 13.5k

### Determining Sectional Drag Coefficient Using Propeller Geometry

None of these are useful for you. They all pertain to a 3D full aircraft. Please go back and cite specific equation numbers in the reference you cited. The airfoil local drag coefficient appears in ...
• 13.1k
Accepted

### In which position does Starship wings produce the most drag?

In the subsonic re-entry phase, Starship is basically falling free from the sky laying on its belly with the forward (upper) and rear (lower) fins stabilising the free fall and keeping it parallel to ...
• 13.5k

### In a straight and level flight if thrust is equal to drag how is aircraft moving forward?

Drag is produced by moving through the air- more speed means more drag. Thrust is the motive force that pushes the plane through the air- more thrust means more push. At cruise, push equals drag and ...
• 21.3k
1 vote

### Range, Endurance and Fuel Cost Savings of an Aircraft

At a minimum, you need to vary alpha to match lift at the same flight condition and then compare the drag coefficients. Comparing drag at different lift is meaningless. Both analyses should be ...
• 13.1k
1 vote

### Is induced drag only created by wingtip vortices induced downwash?

There is a very common form of incorrect reasoning on display here. In a steady flow we observe two apparently distinct phenomena A and B. We then ask which is cause and which effect. This is almost ...
• 211
1 vote

### Is induced drag only created by wingtip vortices induced downwash?

I really don't know why they waste time and effort in the "PHAK" writing and teaching this stuff. Fundamental in aviation is that the moving aircraft interacts with the air, producing drag. ...
• 20.6k

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